U.S. patent application number 13/778222 was filed with the patent office on 2014-08-28 for fuel nozzle for reducing modal coupling of combustion dynamics.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. The applicant listed for this patent is GENERAL ELECTRIC COMPANY. Invention is credited to Gregory Allen Boardman, Ronald James Chila, Sarah Lori Crothers, James Harold Westmoreland, III.
Application Number | 20140238026 13/778222 |
Document ID | / |
Family ID | 51349652 |
Filed Date | 2014-08-28 |
United States Patent
Application |
20140238026 |
Kind Code |
A1 |
Boardman; Gregory Allen ; et
al. |
August 28, 2014 |
FUEL NOZZLE FOR REDUCING MODAL COUPLING OF COMBUSTION DYNAMICS
Abstract
A fuel nozzle includes a center body that extends axially along
an axial centerline for a length. A shroud circumferentially
surrounds the center body for at least a portion of the length of
the center body. A plurality of helical passages circumferentially
surround the center body along at least a portion of the length of
the center body, and a fuel port in each helical passage has a
different convective time.
Inventors: |
Boardman; Gregory Allen;
(Greer, SC) ; Westmoreland, III; James Harold;
(Greer, SC) ; Crothers; Sarah Lori; (Greenville,
SC) ; Chila; Ronald James; (Greenfield Center,
NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GENERAL ELECTRIC COMPANY |
Schenectady |
NY |
US |
|
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
51349652 |
Appl. No.: |
13/778222 |
Filed: |
February 27, 2013 |
Current U.S.
Class: |
60/742 |
Current CPC
Class: |
F23R 2900/00014
20130101; F23R 3/28 20130101; F23R 3/286 20130101; F02C 7/24
20130101 |
Class at
Publication: |
60/742 |
International
Class: |
F02C 7/24 20060101
F02C007/24; F23R 3/28 20060101 F23R003/28 |
Claims
1. A fuel nozzle, comprising: a. a center body that extends axially
along an axial centerline for a length; b. a shroud that
circumferentially surrounds the center body for at least a portion
of the length of the center body; c. a plurality of walls that
extend radially between the center body and the shroud; d. a
plurality of helical passages at least partially defined by the
center body, the shroud, and the plurality of walls, wherein each
helical passage circumferentially surrounds the center body along
at least a portion of the length of the center body; and e. a fuel
port in each helical passage, wherein each fuel port has a
different axial position in each helical passage.
2. The fuel nozzle as in claim 1, further comprising a fuel plenum
inside the center body.
3. The fuel nozzle as in claim 1, wherein the shroud extends
axially downstream from the plurality of walls.
4. The fuel nozzle as in claim 1, wherein the shroud defines a
diameter, and the diameter decreases downstream from the plurality
of walls.
5. The fuel nozzle as in claim 1, wherein each wall is angled
greater than approximately 30 degrees with respect to the axial
centerline.
6. The fuel nozzle as in claim 1, wherein each wall extends axially
upstream from the shroud.
7. The fuel nozzle as in claim 1, wherein each fuel port provides
fluid communication through the center body into a different
helical passage.
8. The fuel nozzle as in claim 1, wherein each fuel port comprises
a conical outer surface that extends radially into each helical
passage.
9. The fuel nozzle as in claim 1, wherein each fuel port is
equidistant from adjacent walls.
10. A fuel nozzle, comprising: a. a center body that extends
axially along an axial centerline for a length; b. a shroud that
circumferentially surrounds the center body for at least a portion
of the length of the center body; c. a plurality of helical
passages that circumferentially surround the center body along at
least a portion of the length of the center body; and d. a fuel
port in each helical passage, wherein each fuel port has a
different convective time.
11. The fuel nozzle as in claim 10, wherein the shroud extends
axially downstream from the plurality of helical passages.
12. The fuel nozzle as in claim 10, wherein the shroud defines a
diameter, and the diameter decreases downstream from the plurality
of helical passages.
13. The fuel nozzle as in claim 10, wherein each helical passage is
angled greater than approximately 30 degrees with respect to the
axial centerline.
14. The fuel nozzle as in claim 10, wherein each helical passage
extends axially upstream from the shroud.
15. The fuel nozzle as in claim 10, wherein each fuel port
comprises a conical outer surface that extends radially into each
helical passage.
16. A gas turbine, comprising: a. a compression section; b. a
combustion section downstream from the compression section; c. a
turbine section downstream from the combustion section; d. a fuel
nozzle in the combustion section; e. a plurality of helical
passages that extend axially in the fuel nozzle; and f. a fuel port
in each helical passage, wherein each fuel port has a different
convective time.
17. The gas turbine as in claim 16, further comprising a shroud
that circumferentially surrounds the plurality of helical passages,
wherein the shroud extends axially downstream from the plurality of
helical passages.
18. The gas turbine as in claim 16, further comprising a shroud
that circumferentially surrounds the plurality of helical passages,
wherein the shroud defines a diameter, and the diameter decreases
downstream from the plurality of helical passages.
19. The gas turbine as in claim 16, further comprising a shroud
that circumferentially surrounds the plurality of helical passages,
wherein each helical passage extends axially upstream from the
shroud.
20. The gas turbine as in claim 16, wherein each fuel port
comprises a conical outer surface that extends radially into each
helical passage.
Description
FIELD OF THE INVENTION
[0001] The present invention generally involves a fuel nozzle for
reducing modal coupling of combustion dynamics. In particular
embodiments, the fuel nozzle and method may be incorporated into a
gas turbine or other turbomachine.
BACKGROUND OF THE INVENTION
[0002] Combustors are commonly used in industrial and commercial
operations to ignite fuel to produce combustion gases having a high
temperature and pressure. For example, gas turbines and other
turbomachines typically include one or more combustors to generate
power or thrust. A typical gas turbine used to generate electrical
power includes an axial compressor at the front, multiple
combustors around the middle, and a turbine at the rear. Ambient
air enters the compressor as a working fluid, and the compressor
progressively imparts kinetic energy to the working fluid to
produce a compressed working fluid at a highly energized state. The
compressed working fluid exits the compressor and flows through one
or more fuel nozzles in the combustors where the compressed working
fluid mixes with fuel before igniting in a combustion chamber to
generate combustion gases having a high temperature and pressure.
The combustion gases flow to the turbine where they expand to
produce work. For example, expansion of the combustion gases in the
turbine may rotate a shaft connected to a generator to produce
electricity.
[0003] Combustion instabilities may occur during operation when one
or more acoustic modes of the gas turbine are excited by the
combustion process. The excited acoustic modes may result in
periodic oscillations of system parameters (e.g., velocity,
temperature, pressure) and processes (e.g., reaction rate, heat
transfer rate). For example, one mechanism of combustion
instabilities may occur when the acoustic pressure pulsations cause
a mass flow fluctuation at a fuel port which then results in a
fuel-air ratio fluctuation in the flame. When the resulting
fuel/air ratio fluctuation and the acoustic pressure pulsations
have a certain phase behavior (e.g., approximately in-phase), a
self-excited feedback loop may result. This mechanism, and the
resulting magnitude of the combustion dynamics, depends at least in
part on the delay between the time that the fuel is injected
through the fuel nozzles and the time when the fuel reaches the
combustion chamber and ignites, defined as convective time (Tau).
When the convective time increases, the frequency of the combustion
instabilities decreases, and when the convective time decreases,
the frequency of the combustion instabilities increases.
[0004] The resulting combustion dynamics may reduce the useful life
of one or more combustor and/or downstream components. Therefore, a
fuel nozzle that varies the convective time would be useful to
enhancing the thermodynamic efficiency of the combustors,
protecting against accelerated wear, promoting flame stability,
and/or reducing undesirable emissions over a wide range of
operating levels.
BRIEF DESCRIPTION OF THE INVENTION
[0005] Aspects and advantages of the invention are set forth below
in the following description, or may be obvious from the
description, or may be learned through practice of the
invention.
[0006] One embodiment of the present invention is a fuel nozzle
that includes a center body that extends axially along an axial
centerline for a length. A shroud circumferentially surrounds the
center body for at least a portion of the length of the center
body. A plurality of walls extend radially between the center body
and the shroud. A plurality of helical passages at least partially
defined by the center body, the shroud, and the plurality of walls,
circumferentially surround the center body along at least a portion
of the length of the center body. A fuel port in each helical
passage has a different axial position in each helical passage.
[0007] In an alternate embodiment of the present invention, a fuel
nozzle includes a center body that extends axially along an axial
centerline for a length. A shroud circumferentially surrounds the
center body for at least a portion of the length of the center
body. A plurality of helical passages circumferentially surround
the center body along at least a portion of the length of the
center body, and a fuel port in each helical passage has a
different convective time.
[0008] The present invention may also include a gas turbine having
a compression section, a combustion section downstream from the
compression section, and a turbine section downstream from the
combustion section. A fuel nozzle is in the combustion section, and
a plurality of helical passages extend axially in the fuel nozzle.
A fuel port in each helical passage has a different convective
time.
[0009] Those of ordinary skill in the art will better appreciate
the features and aspects of such embodiments, and others, upon
review of the specification.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] A full and enabling disclosure of the present invention,
including the best mode thereof to one skilled in the art, is set
forth more particularly in the remainder of the specification,
including reference to the accompanying figures, in which:
[0011] FIG. 1 is a simplified side cross-section view of an
exemplary gas turbine according to various embodiments of the
present invention;
[0012] FIG. 2 is a simplified side cross-section view of an
exemplary combustor according to various embodiments of the present
invention;
[0013] FIG. 3 is a perspective view of a fuel nozzle according to
one embodiment of the present invention;
[0014] FIG. 4 is a side cross-section view of the fuel nozzle shown
in FIG. 3; and
[0015] FIG. 5 is a side cross-section view of an exemplary helical
passage and fuel port shown in FIGS. 3 and 4.
DETAILED DESCRIPTION OF THE INVENTION
[0016] Reference will now be made in detail to present embodiments
of the invention, one or more examples of which are illustrated in
the accompanying drawings. The detailed description uses numerical
and letter designations to refer to features in the drawings. Like
or similar designations in the drawings and description have been
used to refer to like or similar parts of the invention. As used
herein, the terms "first," "second," and "third" may be used
interchangeably to distinguish one component from another and are
not intended to signify location or importance of the individual
components. The terms "upstream," "downstream," "radially," and
"axially" refer to the relative direction with respect to fluid
flow in a fluid pathway. For example, "upstream" refers to the
direction from which the fluid flows, and "downstream" refers to
the direction to which the fluid flows. Similarly, "radially"
refers to the relative direction substantially perpendicular to the
fluid flow, and "axially" refers to the relative direction
substantially parallel to the fluid flow.
[0017] Each example is provided by way of explanation of the
invention, not limitation of the invention. In fact, it will be
apparent to those skilled in the art that modifications and
variations can be made in the present invention without departing
from the scope or spirit thereof For instance, features illustrated
or described as part of one embodiment may be used on another
embodiment to yield a still further embodiment. Thus, it is
intended that the present invention covers such modifications and
variations as come within the scope of the appended claims and
their equivalents.
[0018] Various embodiments of the present invention include a fuel
nozzle for reducing modal coupling of combustion dynamics. The fuel
nozzle generally includes a plurality of helical passages that
extend axially in the fuel nozzle, with at least one fuel port in
each helical passage. In particular embodiments, the fuel nozzle
may include a center body, a shroud that circumferentially
surrounds at least a portion of the center body, and/or a plurality
of walls that extend radially between the center body and the
shroud to at least partially define the helical passages. Each fuel
port may have a different axial position in the respective helical
passages so that each fuel port has a different convective time.
The different convective times alter the frequency and/or amplitude
relationship between fuel nozzles and/or combustors to reduce the
coherence of the combustion system as a whole, diminishing any
coupling between fuel nozzles and/or combustors. As used herein,
coherence refers to the strength of the linear relationship between
two (or more) dynamic signals, which is strongly influenced by the
degree of frequency overlap between them. As a result, various
embodiments of the present invention may reduce the ability of the
combustor tone to cause a vibratory response in downstream
components. Although exemplary embodiments of the present invention
will be described generally in the context of combustion dynamics
in a gas turbine for purposes of illustration, one of ordinary
skill in the art will readily appreciate that embodiments of the
present invention may be applied to any combustion dynamics and are
not limited to a gas turbine unless specifically recited in the
claims.
[0019] Referring now to the drawings, wherein identical numerals
indicate the same elements throughout the figures, FIG. 1 provides
a simplified side cross-section view of an exemplary gas turbine 10
that may incorporate various embodiments of the present invention.
As shown, the gas turbine 10 may generally include an inlet section
12, a compression section 14, a combustion section 16, a turbine
section 18, and an exhaust section 20. The inlet section 12 may
include a series of filters 22 and one or more fluid conditioning
devices 24 to clean, heat, cool, moisturize, de-moisturize, and/or
otherwise condition a working fluid (e.g., air) 28 entering the gas
turbine 10. The cleaned and conditioned working fluid 28 flows to a
compressor 30 in the compression section 14. A compressor casing 32
contains the working fluid 28 as alternating stages of rotating
blades 34 and stationary vanes 36 progressively accelerate and
redirect the working fluid 28 to produce a continuous flow of
compressed working fluid 38 at a higher temperature and
pressure.
[0020] The majority of the compressed working fluid 38 flows
through a compressor discharge plenum 40 to one or more combustors
42 in the combustion section 16. A fuel supply 44 in fluid
communication with each combustor 42 supplies a fuel to each
combustor 42. Possible fuels may include, for example, blast
furnace gas, coke oven gas, natural gas, methane, vaporized
liquefied natural gas (LNG), hydrogen, syngas, butane, propane,
olefins, diesel, petroleum distillates, and combinations thereof.
The compressed working fluid 38 mixes with the fuel and ignites to
generate combustion gases 46 having a high temperature and
pressure.
[0021] The combustion gases 46 flow along a hot gas path through a
turbine 48 in the turbine section 18 where they expand to produce
work. Specifically, the combustion gases 46 may flow across
alternating stages of stationary nozzles 50 and rotating buckets 52
in the turbine 48. The stationary nozzles 50 redirect the
combustion gases 46 onto the next stage of rotating buckets 52, and
the combustion gases 46 expand as they pass over the rotating
buckets 52, causing the rotating buckets 52 to rotate. The rotating
buckets 52 may connect to a shaft 54 that is coupled to the
compressor 30 so that rotation of the shaft 54 drives the
compressor 30 to produce the compressed working fluid 38.
Alternately or in addition, the shaft 54 may connect to a generator
56 for producing electricity. Exhaust gases 58 from the turbine
section 18 flow through the exhaust section 20 prior to release to
the environment.
[0022] The combustors 42 may be any type of combustor known in the
art, and the present invention is not limited to any particular
combustor design unless specifically recited in the claims. FIG. 2
provides a simplified side cross-section view of an exemplary
combustor 42 according to various embodiments of the present
invention. As shown in FIG. 2, a combustor casing 60 and an end
cover 62 may combine to contain the compressed working fluid 38
flowing to the combustor 42. A cap assembly 64 may extend radially
across at least a portion of the combustor 42, and one or more fuel
nozzles 66 may be radially arranged across the cap assembly 64 to
supply fuel to a combustion chamber 70 downstream from the cap
assembly 64. A liner 72 may circumferentially surround at least a
portion of the combustion chamber 70, and a transition duct 74
downstream from the liner 72 may connect the combustion chamber 70
to the inlet of the turbine 48. An impingement sleeve 76 with flow
holes 78 may circumferentially surround the transition duct 74, and
a flow sleeve 80 may circumferentially surround the liner 72. In
this manner, the compressed working fluid 38 may pass through the
flow holes 78 in the impingement sleeve 76 to flow through an
annular passage 82 outside of the transition duct 74 and liner 72.
When the compressed working fluid 38 reaches the end cover 62, the
compressed working fluid 38 reverses direction to flow through the
fuel nozzles 66 and into the combustion chamber 70.
[0023] FIG. 3 provides a perspective view of an exemplary fuel
nozzle 66 within the scope of various embodiments of the present
invention, and FIG. 4 provides a side cross-section view of the
fuel nozzle 66 shown in FIG. 3. As shown in FIGS. 3 and 4, the fuel
nozzle 66 may include a center body 90 that extends axially along
an axial centerline 92 of the fuel nozzle 66 for a length 94. The
center body 90 may connect to and/or pass through the end cover 62
to provide fluid communication from the end cover 62, through the
cap assembly 64, and into the combustion chamber 70. For example,
the center body 90 may include one or more fluid plenums that
permit fuel, diluent, and/or other additives to flow from the end
cover 62 into the combustion chamber 70. In the particular
embodiment shown in FIGS. 3 and 4, a fuel plenum 96 extends axially
inside the center body 90 along the length 94 to supply fuel
through the fuel nozzle 66.
[0024] The fuel nozzle 66 may also include a shroud 100 that
circumferentially surrounds the center body 90 for at least a
portion of the length 94 of the center body 90. The shroud defines
a diameter 102 inside the shroud 100. A plurality of walls 104 may
extend radially between the center body 90 and the shroud 100. In
this manner, the center body 90, shroud 100, and walls 104 may
combine to at least partially define a plurality of helical
passages 106 that circumferentially surround the center body 90
along at least a portion of the length 94 of the center body 90.
The helical passages 106 impart swirl to the compressed working
fluid 38 flowing through the fuel nozzle 66. In the particular
embodiment shown in FIGS. 3 and 4, each wall 104 and/or helical
passage 106 may extend axially upstream from the shroud 100 to
receive or scoop the compressed working fluid 38 into the fuel
nozzle 66. Alternately, or in addition, the shroud 100 may extend
axially downstream from the walls 104 and/or helical passages 106,
and the diameter 102 of the shroud 100 may decrease downstream from
the walls 104 and/or helical passages 106 to enhance continued
swirl of the compressed working fluid 38 flowing out of the fuel
nozzle 66 and entering the combustion chamber 70.
[0025] The number and pitch angle of the walls 104 and helical
passages 106 may be varied to change the overall mixing length
and/or exiting swirl strength. In the particular embodiment shown
in FIGS. 3 and 4, for example, the fuel nozzle 66 includes twelve
walls 104 that form twelve helical passages 106 angled at
approximately 50 degrees around the center body 90. In other
embodiments within the scope of the present invention, the number
of walls may vary between 3 and 15 or more, and the pitch angle may
vary between approximately 10 degrees and 80 degrees. However,
embodiments of the present invention are not limited to any
particular number of walls 104 and/or helical passages 106 and/or
pitch angles unless specifically recited in the claims.
[0026] As shown in FIGS. 3 and 4, each helical passage 106 includes
at least one fuel port 108 to provide fluid communication from the
fuel plenum 96, through the center body 90, and into each helical
passage 106. The fuel ports 108 allow a fuel 109 to be injected
into each helical passage 106 and swirl with the compressed working
fluid 38 to enhance mixing between the fuel 109 and the compressed
working fluid 38 before reaching the combustion chamber 70. The
convective time (Tau) associated with each fuel port 108 is
directly proportional to the distance that the fuel 109 travels
before reaching the combustion chamber 70. This distance in turn is
a function of the pitch angle (i.e., length) of each helical
passage 106 and axial position of each fuel port 108 in the fuel
nozzle 66. A shorter convective time reduces the amount of mixing
between the fuel 109 and the compressed working fluid 38 flowing
through the helical passages 106. A longer convective time enhances
the mixing between the fuel 109 and the compressed working fluid
38, but may also increase the reactivity of the fuel 109 and create
conditions conducive to premature ignition before the fuel 109
reaches the combustion chamber 70.
[0027] In the particular embodiment shown in FIGS. 3 and 4, each
fuel port 108 has a different axial position in each helical
passage 106, producing a corresponding different convective time
for each fuel port 108. The different convective times result in a
corresponding different frequency for each helical passage 108. As
a result, the frequencies produced by the fuel nozzle 66 are more
diffuse and have smaller amplitudes, similar to white noise,
reducing the conditions conducive to combustion instabilities.
[0028] FIG. 5 provides a side cross-section view of an exemplary
helical passage 106 and fuel port 108 shown in FIGS. 3 and 4. As
shown, the fuel port 108 may be equidistant from adjacent walls 104
and may include a conical outer surface 110 that extends radially
into each helical passage 106. As a result, the combination of the
helical passage 106 and conical outer surface 110 may create a
double vortex of compressed working fluid 38 flowing through the
helical passages 106 to enhance mixing with the fuel 109 injected
into the helical passage 106. In particular embodiments, the fuel
ports 108 may angled in the helical passage 106 at a compound
angle. Alternately, or in addition, the helical passages 106 may
include turbulators to disrupt the laminar flow of the fuel 109 and
compressed working fluid 38 through the fuel nozzle 66.
[0029] The various embodiments described and illustrated with
respect to FIGS. 1-5 may provide one or more of the following
advantages over existing combustors 42. Specifically, the more
diffuse and smaller amplitude frequencies associated with the
helical passages 106 reduce the conditions conducive to combustion
instabilities, thereby reducing coherence and/or modal coupling of
combustion dynamics. As a result, the various embodiments described
herein may enhance thermodynamic efficiency, promote flame
stability, and/or reduce undesirable emissions over a wide range of
operating levels, without detrimentally impacting the life of the
downstream hot gas path components.
[0030] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defined by the
claims, and may include other examples that occur to those skilled
in the art. Such other examples are intended to be within the scope
of the claims if they include structural elements that do not
differ from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from
the literal language of the claims.
* * * * *